The present invention generally relates to aircraft armament apparatus and, in a preferred embodiment thereof, more particularly relates to the mounting of machine guns, representatively 30 mm machine guns, on light aircraft such as helicopters.
The external mounting on aircraft of weaponry such as machine guns has heretofore carried with it a variety of structural, operational and safety limitations and disadvantages. To a great extent these problems have been eliminated by using a honeycombed metal support plank such as that illustrated and described in U.S. Pat. No. 5,419,234 to Sanderson. As illustrated in such patent, 40 mm machine guns are mounted on opposite support plank ends which project outwardly from the cabin area of a helicopter.
A particularly difficult external aircraft mounting problem is presented by the much higher recoil 30 mm machine gun. In previously proposed nonplank-based external aircraft mounting systems for 30 mm machine guns, several problems, limitations and disadvantages have been present. For example, due to the high recoil forces generated by firing the 30 mm machine gun, their external aircraft mounts have tended to be quite complexxe2x80x94an undesirable characteristic arising from the need to protect the xe2x80x9clightxe2x80x9d helicopter (such as an MD 500 or Bell 206 helicopter) from structural damage from recoil forces, and to prevent loss of pilot control of the aircraft during gun firing. Attempts to design an external aircraft mount structure for the 30 mm machine structure have heretofore not been entirely successful in either of these areas.
Other problems, limitations and disadvantages presented in the use of both aircraft and ground-mounted 30 mm machine guns have to do with the construction and operation of the gun itself. The three primary areas of such problems, limitations and disadvantages in conventionally constructed 30 mm machine guns arise from (1) their complex construction, (2) their heretofore unavoidable high firing recoil forces, and (3) the difficulty in field servicing the guns.
The complex construction of traditionally configured 30 mm machine guns can lead to reliability problems and difficult and expensive fabrication operations. The high recoil forces of conventional 30 mm machine guns undesirably diminishes their firing controllability and accuracy and, as mentioned above, has made it quite difficult to mount 30 mm machine guns on light aircraft such as helicopters. Further, the difficulty in field servicing the guns typically requires that they be uncoupled from the aircraft and taken to a special maintenance facility to be worked on by a specialized technician having an aircraft mechanic/ordnance skill level. This has been true even for routine gun cleaning and maintenance services. Additionally, to simply clean a conventionally constructed 30 mm machine gun it has to be taken nearly completely apartxe2x80x94a tedious task entailing removing countless screws, bolts and other fasteners and then replacing them after the gun cleaning task is completed.
From the foregoing it can readily be seen that a need exists for a 30 mm machine gun that eliminates or at least substantially reduces the above-mentioned problems, limitations and disadvantages commonly associated with 30 mm machine guns of conventional construction. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a machine gun, representatively a 30 mm machine gun, is provided with a variety of unique structural and operational features which serve to (1) reduce the complexity of the gun, (2) make it relatively easy to service in the field, and (3) substantially reduce its recoil to thereby facilitate its mountability on light aircraft such as helicopters, and improve its firing controllability and accuracy. The gun is illustratively secured, via a rollered mounting cradle, to the outer end of a support plank structure extending transversely through the cabin area of an aircraft, but may be supported in other manners in a variety of other aircraft and ground-based mounting applications.
In its preferred embodiment, the machine gun basically comprises a body upon which a barrel is mounted, the barrel longitudinally extending forwardly and rearwardly along a firing axis. The body is supported by a cradle and feed structure unit for rearward recoil movement and forward counter-recoil movement relative to the cradle and feed structure unit in response to the firing of the gun. The feed structure part of the unit is operative to position successive cartridges for retrieval and chambering in the barrel for firing therein. An operating rod structure is carried by the body for driven movement relative thereto cyclically in forward and rearward directions in response to firing of the gun, and a resilient recoil system is provided for absorbing the rearward recoil and forward counter-recoil forces of the gun. Firing apparatus is provided for firing each chambered cartridge, the firing of each cartridge causing a rearward recoil movement and subsequent forward counter-recoil movement of the gun body relative to the stationary feed and cradle apparatus.
Ammunition handling means are carried by the gun body and are operative to deliver cartridges from the feed structure to the barrel for firing therein, and then extracting and ejecting the spent casings of the fired cartridges. Representatively, the ammunition handling means include a bolt member carried by the operating rod structure rearwardly of the feed structure for cyclical forward and rearward movement with the operating rod structure toward and away from the feed structure, the bolt member having first and second extractor means thereon for releasably receiving and retaining rear cartridge casing rim portions.
A bolt face member is carried by the bolt member for movement relative thereto in first and second opposite directions transverse to the barrel, the bolt face member having ejector means thereon for releasably circumscribing a rear cartridge casing end portion. Cooperating means are provided on the bolt face member and the gun body for moving the bolt face member in the first direction relative to the bolt member in response to movement of the bolt member toward the feed structure, and for moving the bolt face member in the second direction relative to the bolt member in response to movement of the bolt member away from the feed structure. Representatively, these cooperating means include a cam track formed in the body with a pivotally spring-loaded switch plate member attached, and a roller structure carried on the bolt face member and received in the cam track for guided rolling movement therealong.
The relatively simple bolt; member/bolt face member structure performs several ammunition handling functions during the firing of the gunxe2x80x94namely, (1) extracting a first cartridge from the feed structure, (2) chambering the extracted first cartridge in the barrel, (3) extracting a second cartridge from the feed structure while extracting the spent casing of the first cartridge, after firing thereof, from the barrel, and (4) moving the extracted second cartridge into a chambering alignment position in a manner causing the extracted second cartridge to engage and forcibly eject the spent casing from the ammunition handling means by ejectors mounted on the bolt face member.
Cooperatively engaged first and second structures are respectively disposed on the gun body and the feed structure for operating the feed structure in response to forward and rearward movement of the gun body relative to the stationary feed structure. Because the movement of the gun body relative to the feed apparatus operates the feed apparatus, no complicated timing system is needed.
Representatively, a cam track slot having an angled central portion is formed in a top side portion of the gun body and slidingly receives a cam follower pin which depends from a rotatable feed drum portion of the feed structure. The feed drum is connected by a one way clutched gear train to a splined drive shaft which extends parallel to the barrel and is rotationally locked to a sprocket structure that delivers individual cartridges from a cartridge belt to the bolt structure. The sprocket structure is slidable along the splined drive shaft, between front and rear limit positions and is spring-biased toward its rear limit position. A depressible bolt face sensor switch is carried on a rear side portion of the sprocket and is forwardly struck and depressed by the bolt face structure during firing of the gun.
During the firing of the gun, the rearward recoil of the gun body relative to the feed structure causes the cam pin/cam track slot interaction to rotate the feed drum in a first direction which back-indexes the ratcheted gear train without rotating the splined drive shaft, and the forward counter-recoil movement of the gun causes the cam pin/cam track slot interaction to rotate the feed drum in a second direction which rotationally drives the gear train to rotationally drive the sprocket structure and advance the ammunition belt one cartridge.
The operating rod structure of the gun preferably comprises a spaced pair of hollow left and right operating rods extending parallel to the gun barrel. The operating rods have closed front ends, and open rear ends anchored to an operating rod body slidingly carried within the gun body for forward and rearward movement relative thereto. The previously mentioned bolt structure is carried by the operating rod body for forward and rearward movement therewith within the gun body. Guide rods extend forwardly through the operating rods, and springs carried by the guide rods resiliently bias the operating rod structure to a front limit position within the gun body. When the gun is fired, pressurized gas from the fired cartridge is used to rearwardly drive the operating rod structure, against the resilient resistance of the guide rod springs which function to return the operating rod structure, and the bolt structure which it carries, to their forward limit positions.
According to a feature of the invention, the bolt structure is cyclically movable in forward and rearward directions within the gun body between a front limit position disposed rearwardly of the front limit position of the operating structure, and a rear limit position. A lock structure is associated with the operating rod structure and the bolt structure and is shiftable relative thereto between (1) a first position in which the lock structure releasably latches the operating rod structure and the bolt structure for conjoint forward and rearward movement relative to the gun body, and (2) a second position in which the lock structure releasably interlocks with the gun body in a manner preventing forward and rearward movement of the bolt structure relative to the gun body, and unlatches the operating rod structure and the bolt structure to permit forward movement of the rod operating structure relative to the gun body and bolt structure.
First means are provided for shifting the lock structure from its first position to its second position in response to the bolt structure reaching its front limit position, and second means are provided for shifting the lock structure from its second position to its first position in response to rearward movement of the operating structure away from its front limit position.
When the bolt structure with the bolt face structure attached thereto reaches its forward limit position, and is locked therein by the shifted lock member, the bolt face structure depresses the aforementioned bolt sensor switch. When the forwardly moving operating rod structure finishes the lock movement and the lock structure reaches its front limit position it causes a second switch to close. only when both of these two switches close, assuring that the bolt is locked to the gun body and the gun is within the feed system, can the gun be fired.
In response to the operating rod structure reaching its front limit position, with the bolt structure locked to the gun body by the shifted lock member, a secondary mass member slidably carried behind the operating rod body portion forwardly strikes the operating rod body in a manner inhibiting undesirable rearwardly directed impact bounce-back movement of the operating rod structure which might unlock the bolt structure from the gun body. The secondary mass member is spring-biased rearwardly away from the operating rod body portion until the operating rod structure stops upon reaching its front limit position.
As the operating rods are cycled back and forth during firing of the gun, an electrical brush member slides along an electrically insulative strip on the outer side surface of one of the operating rods, the strip having an electrically conductive hot shoe portion at one end thereof and electrically coupled to the operating rod body portion via a wire imbedded in the insulative material. Shortly before the operating rod body reaches its front limit position the brush slides onto the hot shoe as the operating rod body closes the second firing switch. An electrical switch circuit receives a signal from the bolt face sensor switch when it is closed by the bolt face structure and responsively transmits electrical current to the brush to permit the gun to be fired when both switches close. In this manner, electrical firing power is sent to the gun only when neededxe2x80x94it need not be maintained continuously as in most conventional machine gun electrical firing systems.
The recoil system resiliently absorbs the recoil and counter-recoil forces of the gun as it moves rearwardly and forwardly relative to the stationary cradle mounting structure which supports the gun and holds the feed structure. In its preferred embodiment, the recoil system includes a recoil member fixedly securable to the stationary mounting structure, the gun body being movable forwardly and rearwardly relative to the recoil member, the recoil member having opposite front and rear portions. The rear portion of the recoil member is preferable formed from a resilient material.
The recoil system also representatively includes a counter recoil shock absorber anchored to the gun body and having a forwardly projecting depressible plunger member engageable with the rear portion of the recoil member; a recoil spring stop member anchored to the gun body forwardly of the recoil shock absorber, with the recoil member being disposed between the recoil shock absorber and the recoil spring stop member; a rod member having a first end anchored to the recoil member, and a second and slidably extending forwardly through the recoil spring stop member; a recoil damper anchored to the gun body forwardly of the recoil spring stop member and having a rearwardly extending depressible plunger member secured to the second end of the rod member; and a spring structure carried by the rod member and being compressible between the recoil member and the recoil spring stop member in response to rearward movement of the gun body relative to the recoil member.
In a pre-firing condition of the gun the operating rod structure is held in a rearward position thereof, against the resilient force of the guide rod springs, by a specially designed sear system. The sear system utilizes pivotally mounted sear members having roller portions thereon. The sear members are pivotally biased toward first positions in which they engage inner portions of arcuate, forwardly facing ledges formed on the closed front ends of the two operating rods. In such first positions the rollers are below xe2x80x9cjamxe2x80x9d angles of the ledge/roller interface areas and prevent the front ends of the operating rods from moving forwardly past the rollers.
To unlatch the sear system from the operating rods, and permit the operating rod structure to be spring-driven forwardly to initiate firing of the gun, a sear solenoid is electrically energized to forcibly move a core portion thereof. The solenoid core portion is coupled to the pivotable sear members through a mechanically advantaged linkage system which is driven by the core portion to pivot the sear members to second positions just above the pinch angle of the operating rod ledges, but not out of contact with the ledges. The arcuate ledges then rotate the sear member rollers out of engagement therewith to allow the operating structure to be forwardly driven to initiate firing of the gun. During firing of the gun, each time the ledges rearwardly pass the sear member rollers they permit the rollers to be moved inwardly to their second positions and then kick the rollers back outwardly from the ledges as the ledges forwardly pass the rollers.
During certain pre-firing conditions of the gun, such as when it is being reloaded, the operating rods are stationary in their forwardmost positions within the gun body. To move them back to their xe2x80x9con searxe2x80x9d ready-to-fire positions a specially designed charger system is provided.
Unlike conventional charger systems, the charger system of the present invention (which preferably carries the previously described sear system) is carried on the gun body for recoil and counter-recoil movement therewith. Accordingly, the charger system adds to the overall recoiling and counter-recoiling mass to advantageously lesson the recoil and counter-recoil forces.
Additionally, in contrast to conventional charger systems, the charger system of the present invention does not have a member which must engage and rearwardly move the operating structure to its xe2x80x9con searxe2x80x9d position and then be forwardly returned to its starting system to get it out of the way of the operating structure before the gun can be fired. Instead, the charger system of the present invention, in a preferred embodiment thereof utilizes a motor-driven pinion gear which is shiftable transversely to one of the operating rods into and out of driving engagement with a gear rack portion formed on a flattened exterior side surface portion thereof.
The pinion gear is rotationally driven, via an intermediate gear train, by an electric charger motor and a portion of the pinion gear forms the shiftable core portion of an electrical solenoid. When the charger motor and solenoid are energized with the operating rods in their forwardmost positions within the gun body, the pinion gear is first shifted into driving engagement with the gear rack and then rotationally driven to rearwardly move the operating structure to its xe2x80x9con searxe2x80x9d position at which time it is latched in such position by the sear system.
During rearward charging movement of the operating rod structure by the charger system, an electrically charged brush slides along a strip of electrically insulative material on the other operating rod. When the operating rod structure reaches its xe2x80x9con searxe2x80x9d position, the brush moves off the front end of the strip and is grounded to its associated operating rod. This grounding responsively de-energizes the charger motor to thereby stop the rearward motion of the operating structure and shift the pinion gear out of driving engagement with its associated operating rod rack.
In addition to the recoil reduction achieved by mounting the charger/sear system on the gun body for recoil and counter-recoil movement therewith, various other unique recoil reduction features are incorporated into the machine gun of the present invention.
For example, when the gun is fired the gun body rearwardly recoils. Subsequently, the operating rod structure is gas-driven rearwardly relative to the rearwardly moving gun body at a velocity greater than the velocity of the rearwardly recoiling gun body. Prior to the gun body beginning its forward counter-recoil stroke, the bolt structure carried on the rearwardly moving operating rod body portion strikes a resilient bolt buffer assembly carried on a rear interior end portion of the gun body.
This causes the operating structure and bolt structure to forwardly rebound in a manner such that the operating and bolt structures reach their front limit positions, and fire the gun, while the body is moving forwardly through its counter-recoil stroke. Thus, the firing recoil force is offset to a substantial degree by the mass of the still forwardly moving gun.
Another feature that desirably reduces the recoil force of the gun is a specially designed muzzle brake removably secured to the front end of the gun barrel. The muzzle brake has a hollow body coaxial with the firing axis of the barrel, and open front and rear ends. An axially spaced series of gas discharge openings are formed in the side wall of the muzzle brake body between its inner and outer surfaces, with the flow areas of the gas discharge openings progressively increasing in a rear-to-front direction along the length of the muzzle brake body.
The gas discharge openings are sloped rearwardly and laterally outwardly relative to the axis of the muzzle brake body. When the gun is fired, pressurized gas behind the cartridge projectile being expelled from the barrel is vented outwardly through the gas discharge openings, thereby exerting a forward force on the gun which desirably counteracts its rearwardly directed firing recoil force. The unique progressive cross-sectional increase in a forward direction of the gas discharge openings desirably tends to even out this forward force on the gun during pressurized gas expulsion from the muzzle brake gas discharge openings.
Another desirable attribute of the improved gas-operated, electrically fired machine gun of the present invention is that is easily field strippable for inspection, cleaning and maintenance purposes. For example, the gun is provided with a specially designed barrel lock system that permits the barrel to be rapidly installed and removed. To install the barrel, a rear end portion thereof in rearwardly inserted into a front end opening of the gun body.
The inserted barrel is then rotated ninety degrees about its axis to interlock lugs on the outer side of the barrel with corresponding lugs within the interior of the breech of the gun body to prevent axial removal of the inserted barrel. To releasably prevent unlocking rotation of the barrel, the inner end of a pin member transverse to the barrel is radially moved into an exterior side surface recess in the barrel, and the pin member is locked into place by the engagement of a rotatable pin handle with retaining pins in the gun body front end structure.
To subsequently remove the barrel, the pin handle is rotated to free it from the front end retaining pins. The barrel locking pin is then radially withdrawn from the barrel recess, the barrel is rotated to disengage its lugs from the gun body breech lugs, and the barrel is pulled out of the gun body.
According to another serviceability feature of the gun, a rear end cap portion of the hollow gun body is removably secured to the balance of the gun body, representatively by a pair of quick-release ball pins. The previously mentioned resilient bolt buffer structure and rear ends of the guide rods are secured to this removable end portion of the gun body. When the rear gun body end cap portion is removed, the bolt buffer structure and the guide rods and their associated springs come with it. subsequently, and without using any tools, the overall operating rod structure, and the bolt structure which it carries, can simply be pulled rearwardly out of the gun. The gun body preferably has an open bottom side which further facilitates this easy and rapid field strippability of the gun.